Coaxial seals, sometimes called graded seals, are well known. They are conventionally used to make glass seals between terminal pins and a wall of material with a difference in thermal expansion too great to permit the use of a single glass seal. Two glasses are used, the outer glass having a coefficient compatible with the wall material and the inner, a coefficient compatible with the pin. It has been discovered that by using two or more glasses of distinctly different electrical/chemical properties, the resistance of the seal to attack by chemicals corrosive to glass can be greatly enhanced. In particular, in a battery utilizing a lithium-sulfur dioxide system, the resistance to attack can be improved dramatically over that of the glasses individually.
One of the objects of this invention is to provide a glass seal that exhibits a greater resistance to attack than the individual glasses used in making the seal.
Other objects will become apparent to those skilled in the art in the light of the following description and accompanying drawing.